Relation between potential in the band diagram and applied voltage under forward bias


That is very helpful. Thank you.

Just one more question. In the “electrostatics” results, the V’s max and
min values are not what are set in the anode and cathode. For example, if
when forward bias is applied, 2V for anode and 0 for cathode, the max value
could be 1.4 and min value 0.67. Is this because of the built in V of the
PN junction?

Yongming Tu
PhD Candidate
EECS Department
Northwestern University
Evanston, IL

Difference between 2D and 3D CHARGE simulations

You are right. When you are applying a forward bias voltage across a diode, part of the voltage works to lower the barrier at the pn junction. Once the barrier gets removed, the device starts to act like a resistor and any additional voltage drops across the entire device. The drop you see across the device at very large forward bias will be equal to the applied voltage minus the voltage required to put the diode well into forward bias (into the zone where it started to behave like a resistor).